Enantiomers can be produced using various techniques e.g. classical resolution by crystallisation of diastereomeric salts of the racemate, enzymatic resolution, chromatographic separation of the enantiomers, separation of the racemate by chiral chromatography as well as by different enantioselective synthetic techniques.
There is, however, a need to select a suitable combination of process steps as well as suitable conditions of each individual step in order to achieve an enantiomeric purity, which is sufficient to provide a pharmaceutically and economically feasible process.
It is such a process that the present invention sets out to define, and more particularly for the preparation of the (S)-enantiomer of certain 2-ethoxy-3-(4-hydroxyphenyl)propanoic acids and derivatives thereof.